Is it possible to isolate a specific frequency from a sound ?

I recorded sound where I play a certain frequency by interruption (22000 Hz). In the record, there is some noise, not very important, just my computer fan.
Is it possible to amplify the record and isolate the 22000 Hz frequency to have a binary oscillation of the sound like that ?


For normal audio there is usually very little in the frequency range above about 16000 Hz, so a simple high-pass filter set to around 18000 Hz will give pretty good isolation.

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Thanks for your answer. I can’t see the menu you show me. This is what I have.

This is my Audacity project. Could you say me if it’s possible to do it whit this record ?

You just need to click and drag in the Equalization “graph” to create the filter shape. See: Equalization - Audacity Manual

Thanks a lot for your answer ! I recorded a new sample at 20 000 Hz and I successfully isolated the 20 000 Hz frequency. Now I can visualize the sound :

Now, there is a way to visualize the sound like that ?


You will get better isolation if you make the filter more like this:

What are you actually trying to do? What is the purpose?

I’ll second Steve’s suggestion, but don’t make it too narrow. You don’t say what your bit-rate is. Your filter needs to be wide enough to pass the sidebands that result from your modulation of the 20 kHz carrier – roughly 4x the bit rate for the particular modulation scheme you are using.